How to Repair a Leaking Shutoff Valve

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How to repair or replace a leaking water shutoff valve under your sink or toilet.

If you have some simple plumbing skills there are two ways you can repair a leaking shutoff valve under a sink or behind your toilet. Most shutoff valves are multi-turn angle stop valves that have a rubber seat inside that wears out and will not shut off the water completely. They can be soldered to the copper pipe or installed with a compression fitting. You have two options for repairing a leaking shutoff valve; remove the old one and replace it or install a piggyback valve onto the outlet of the leaking shutoff valve.

Multi-Turn Angle Stop

Quarter-Turn Angle Stop

Piggyback Valve or Add-on Repair Valve

Some valves may be threaded onto a chrome or brass nipple. Compression valves may also be used on copper, CPVC, Polybutylene tubing and even PEX tubing. Supply valves may be attached to PEX or Polybutylene tubing directly with an expanded joint or a joint that is crimped with a ring.

Tools and Materials

Adjustable wrench

Pump pliers

Small Tubing Cutter

Small container

Soldering torch

Flame-protecting cloth

Leather Gloves


Emery Cloth

Pipe Dope

Shutoff valve


Typical Angle Stop Shutoff Valve Installation

It’s always a good idea to check the condition of any shutoff valve when you are working on plumbing fixtures like faucets and toilets. If the water does not shut off completely, you should replace it before you need to shut it off in an emergency. It is better to replace the older multi-turn shutoff valves with quarter-turn shutoff valves which are last longer and are easier to use. If only one valve is leaking on a faucet, you should replace both of them at the same time.

Option #1 - Replacing a Water Shutoff Valve on Soldered Copper Piping

1. Turn off the main water shutoff valve for your home. Open a basement faucet and the faucet above your shutoff valve.

2. Disconnect the faucet supply lines using an adjustable wrench. There may be some water left in the lines so place a container to catch any water.

3. If your old valve is soldered to the pipe, hold onto the valve with pump pliers and heat the valve with a propane torch. When the solder melts, twist the valve back and forth while pulling it off. Wipe the end of the pipe with a rag immediately after removing the valve to get rid of old solder. Be sure to wear leather gloves when working with the torch and removing the valve. Use an emery cloth to sand away the solder to get down to the bare copper pipe.

4. To install a new compression valve; slide the compression nut, then the ferrule, onto the copper water pipe. Lubricate the compression threads with a small amount of pipe dope. Tighten until firm with a pair of adjustable wrenches and then turn the wrench an additional 180 degrees.

5. Connect the faucet supply line after the shutoff valve is in place.

6. Turn on the main water supply valve and test the connection for leaks.

Option #2 – Installing an Add-on Repair ValveAn add-on repair valve, also called a piggyback valve, won’t fix the original valve from passing, but it will let you shut off the water to the fixture without having to shut the water off to the entire house each time. The repair valve is connected between the outlet of the original angle or straight stop and then the supply line. This is also a good choice if the original valve is installed with a compression fitting to the copper pipe and it is too close to the wall to cut it off and install a new valve.

You will need to work quickly as water will be flowing through the bad valve. You may want to place a few towels below the valve to absorb any excess water that may spray when the new valve is being installed.

1. Shut off the water supply valve and place a small bucket below it. Loosen the packing nut slightly to allow the water to drain into the bucket. Disconnect the supply line leading to the toilet or faucet.

2. Quickly place the new repair valve in the open position on top of the old valve. Tighten the compression fitting, then shut off the new valve. Open the old valve all the way and tighten the packing nut.

Leave the old valve open all of the time and only operate the new valve to turn off the water.


Roberta Baxter
Posted on Oct 17, 2011
M 5446
Posted on Oct 17, 2011